This invention relates to a driller which can drill a number of holes automatically in a rice field.
In recent years, the tillage work in the rice field has been made by driving various large-sized agricultural implements and machines such as tractor, combined harvester and thresher, and the like in the rice fields. As the result of this, the rice field surface is hardened by the weight of these machines, and thus there is formed a hardened earth layer of even about 20-30 cm in depth. However, since the depth of a layer cultivated by a tractor is only about 10-15 cm, there remains a hardened earth layer of about 10-15 cm in depth under this cultivated layer. The presence of a remaining hardened earth layer like this not only prevents the aquatic rice from spreading its root in the deep portion of the earth layer, but also hinders the performance of the underdrain formed at a place lower about 100 cm than the rice field surface, namely watering and/or draining performance. Due to this, it becomes impossible or difficult to make a planned and organized water control system, which is indispensable for favorable growth of rice plants, such as supply of water, supplement of water, excess water draining and the like, whereby there takes place such a phenomenon that the soil gets worse and the growth of aquatic rice is hindered.
In view of the fact that any effective means to solve the above mentioned phenomenon have not been proposed yet, the inventor of this invention has done various studies to find such means, and has found that it is effective to solve this problem by drilling longitudinal holes, having a diameter of about 3 cm and a depth of about 30-60 cm, in the rice field, preferably at intervals of about 25-30 cm.